Structure-activity relationship for antineoplastic imidazoacridinones: Synthesis and antileukemic activity in vivo

Article abstract of DOI:10.1021/jm950564r

Synthesis of several new 5-amino-substituted derivatives of 5-amino-6H- imidazo[4,5,1-de]-acridin-6-one bearing in the benzene ring OH, OCH₃, CH₃, tert-butyl, or OCH₂O groups is described. 8-OH-Substituted compounds or dou

Full text of DOI:10.1021/jm950564r

1028
J . Med. Chem. 1996, 39, 1028-1032
Str u ctu r e-Activity Rela tion sh ip for An tin eop la stic Im id a zoa cr id in on es:
Syn th esis a n d An tileu k em ic Activity in Vivo
Wieslaw M. Cholody,† Barbara Horowska,† J olanta Paradziej-Lukowicz,† Sante Martelli,*,‡ and J erzy Konopa†
Department of Pharmaceutical Technology and Biochemistry, Technical University of Gdansk, 80952 Gdansk, Poland, and
Department of Chemical Sciences, University of Camerino, 62032 Camerino, Italy
Received J uly 28, 1995X
Synthesis of several new 5-amino-substituted derivatives of 5-amino-6H-imidazo[4,5,1-de]-
acridin-6-one bearing in the benzene ring OH, OCH3, CH3, tert-butyl, or OCH2O groups is
described. 8-OH-Substituted compounds or double-substituted 7-OH-10-OCH3 compounds
demonstrated potent in vivo activity against murine P388 leukemia. The highest activity was
exhibited by 5-[[2-[[2-(diethylamino)ethyl]amino]ethyl]amino]-8-hydroxy-6H-imidazo[4,5,1-de]-
acridin-6-one (4c).
Sch em e 1a
In tr od u ction
In our recent papers derivatives of 5-amino-6H-
imidazo[4,5,1-de]acridin-6-one were reported as a novel
class of antineoplastic agents.1,2 The compounds sub-
stituted with a hydroxy group in position 8 were found
to be especially active against transplantable murine
tumors: leukemia P388, melanoma B-16, and two colon
adenocarcinomas, C-26 and C-38.3 The derivatives also
presented significant and diversified cytotoxic activity
against 66 human tumor cell lines in the NCI in vitro
screening system. Several of them passed this screen-
ing test and are being considered for further testing on
human tumor xerografts in nude mice (unpublished
data). The most active derivatives are presently exam-
ined extensively in other preclinical tests.
The earlier structure-activity studies revealed that
antitumor activity of 5-amino-6H-imidazo[4,5,1-de]acri-
din-6-one derivatives substituted in position 8 with a
hydroxy or methoxy group is higher than for unsubsti-
tuted compounds.1,2 Structure of the aliphatic side
chain seemed to have only secondary influence, provid-
ing it was an ethylene- or propylenediamine chain.2
The present paper describes the synthesis of new
5-amino-6H-imidazo[4,5,1-de]acridin-6-one derivatives
unsubstituted as well as diversely substituted with
hydroxy or methoxy groups in ring A. It was of interest
to examine how the oxygen substituents, their location
and number, influence biological activity, and for this
reason congeners with hydroxy and methoxy groups in
positions other than 8, as well as with the position 8
blocked by non-oxygen substituents, were prepared.
Compounds possessing, in ring A of imidazoacridinone,
hydroxy, methoxy, or methylenedioxy groups in position
ortho or para to each other which, by some metabolic
transformation, could be transformed into an o- or
p-quinone system could be considered as a special group.
Some structure-activity studies concerning the side
chain of imidazoacridinones are also performed to learn
more about the relevance of side chain structure for
biological activity, as well as susceptibility to modifica-
tion.
a
Reagents: (a) and (c) NH2NH2/Raney Ni/THF; (b) concentrated
HCl/reflux; (d) HCOOH/reflux; (e) HCOOOH/Ni-Al alloy/reflux.
Ch em istr y
A general route to the target 5-[(aminoalkyl)amino]-
6H-imidazo[4,5,1-de]acridin-6-ones 4 is presented in
Scheme 1. The starting substituted 1-chloro-4-nitro-9-
(10H)acridinones 2 were obtained by cyclization of the
corresponding N-phenylanthranilic acids 1 according to
the previously described methods.1,4,5 Two new N-
phenylanthranilic acids, 1a ,b, were prepared by con-
densation of 2,6-dichloro-3-nitrobenzoic acid with a
suitable amine in ethyl alcohol in the presence of
triethylamine. Condensation of acridinones 2 with an
excess of the corresponding amine in N,N-dimethyl-
formamide provided then the desired nitroacridinones
3a -u . Their physical properties are presented in Table
1.
† Technical University of Gdansk.
‡ University of Camerino.
X Abstract published in Advance ACS Abstracts, J anuary 15, 1996.
0022-2623/96/1839-1028$12.00/0 © 1996 American Chemical Society

SAR for Antineoplastic Imidazoacridinones
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5 1029
Ta ble 1. Physical Properties of the 1-Substituted 4-Nitro-9(10H)acridinones 3
no.
X
n
R1
R2
R3
cryst solvent
mp, °C
yield, %
formulaa
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
7-OH
H
7-OH
H
5
2
2
2
2
2
2
2
2
2
2
2
3
2
2
2
2
2
3
2
2
H
H
H
CH3
CH3
H
H
H
H
H
H
H
H
H
H
H
CH3
H
H
CH3
CH3
(CH2)3CH3
CH(CH3)2
CH2CH3
CH2CH3
CH2CH3
CH3
CH2CH3
CH3
CH2CH3
CH2CH3
CH3
CH3
237-239
180-181
213-215
133-134
127-128
200-202
243-245
189-191
166-167
161-162
152-153
208-210
206
167-168
171-172
180-181
204-206
234-235
240-241
198-199
121-122
80
90
70
85
60
85
90
80
95
95
97
96
95
89
77
80
86
60
65
91
90
C20H24N4O4
C21H27N5O3
C21H27N5O4
C18H20N4O3
C18H20N4O4
C23H30N4O4
C21H26N4O4
C19H22N4O4
C20H24N4O4
C21H26N4O5
C19H22N4O5
C21H26N4O5
C20H24N4O5
C22H28N4O6
C20H24N4O5
C18H20N4O5
C21H26N4O6
C20H22N4O5
C19H20N4O5
C20H24N4O3
C23H29N4O3
CH2CH2N(C2H5)2
CH2CH2N(C2H5)2
CH3
7-OH
7-OH
7-OH
6-OH
5-OCH3
5,8-(OCH3)2
5,8-(OCH3)2
6,7-(OCH3)2
6,7-(OCH3)2
6,7,8-(OCH3)3
5-OCH3,8-OH
5-OCH3,8-OH
6,7-(OCH3)2,8-OH
6,7-(-OCH2O-)
6,7-(-OCH2O-)
7-CH3
CH3
(CH2)3CH3
CH(CH3)2
CH2CH3
CH2CH3
CH2CH3
CH3
CH2CH3
CH3
CH2CH3
CH2CH3
CH3
CH2CH3
CH2CH3
CH3
CH2CH3
CH2CH3
acetone
DMF-H2O
benzene-hexane
chloroform-hexane
chloform-hexane
chloroform-hexane
chloroform
chloroform
benzene-hexane
hexane
H
H
H
H
CH2CH3
CH2CH3
CH3
CH2CH3
CH2CH3
3s
3t
3u
7-tert-butyl
H
a
All compounds were analyzed for C, H, N, and the results are within (0.4% of the theoretical values.
Ta ble 2. Physical Properties of the Target Imidazoacridinones 4 from Scheme 1 and Their Activities against P388 Leukemia in Mice
P388 leukemia
opt dose
no.
X
n
R1
R2
R3
mp, °Ca yield, %
formulab
(mg/kg/day) T/C, %c
4a 8-OH
5
2
2
2
2
2
2
2
2
2
2
2
2
3
2
2
2
2
3
2
2
H
H
H
CH3
H
H
CH3
237-239
64
60
50
55
40
66
65
40
50
20
70
20
60
40
20
30
60
56
60
45
35
C21H24N4O2·2HCl·H2O
C22H27N5O·2HCl·1.5H2O
C22H27N5O2·2HCl·H2O
C19H20N4O·2HCl
70
100
100
100
6.25
12.5
25
25
25
50
200
25
50
50
172
130
254
180
210
110
200
127
100
145
130
115
110
115
185
163
115
120
122
115
110
4b
4c 8-OH
4d
4e 8-OH
4f 8-OH
H
CH2CH2N(C2H5)2 165-167
CH2CH2N(C2H5)2 150-151
H
CH3 CH3
CH3 CH3
CH3
CH3
211-213
220-223
168-170
204-206
180-181
179-182
250-252
201-202
220-222
170
C19H20N4O2·2HCl·0.5H2O
C24H30N4O2·2HCl·0.5H2O
C22H26N4O2·2HCl
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
(CH2)3CH3 (CH2)3CH3
CH(CH3)2 CH(CH3)2
4g 8-OH
4h 9-OH
CH2CH3
CH2CH3
CH2CH3
CH2CH3
CH2CH3
CH2CH3
CH3
CH2CH3
CH3
CH2CH3
CH2CH3
CH3
CH2CH3
CH2CH3
CH2CH3
CH2CH3
CH2CH3
CH2CH3
CH3
CH2CH3
CH3
CH2CH3
CH2CH3
CH3
C20H22N4O2·2HCl·H2O
C20H22N4O2·2HCl
4i
4j
10-OH
7,10-(OH)2
C20H22N4O3·2HCl
4k 10-OCH3
C21H24N4O2·2HCl
4l
7,10-(OCH3)2
C22H26N4O3·2HCl
4m 8,9-(OCH3)2
4n 8,9-(OCH3)2
4o 7-OH,10-OCH3
4p 7-OH,10-OCH3
4q 7-OH,8,9-(OCH3)2
C22H26N4O3·2HCl
221-223
195
C21H24N4O3·1.5HCl·H2O
C21H24N4O3·2HCl·H2O
C19H20N4O3·2HCl·H2O
C22H26N4O4·1.5HCl·H2O
C21H22N4O3·2HCl·H2O
C20H20N4O3·2HCl
50
7.3
122-123
186-188
250-252
240-241
210-212
142-143
100
100
50
200
25
4r
4s
4t
8,9-(-OCH2O-)
8,9-(-OCH2O-)
8-CH3
CH2CH3
CH2CH3
CH2CH3
CH2CH3
C21H24N4O·2HCl·H2O
C24H30N4O·2HCl
4u 8-tert-butyl
a
b
All compounds were crystallized from methanol-ether. Elemental analyses are within (0.4% of the theoretical values for C, H, N.
c BDF1 mice were implanted ip with 106 P388 cells on day 0, and each compound was administered ip as aqueous solution on days 1-5.
Each group except control consisted of seven mice. The control group consisted of 10 mice. Values of T/C g 125% indicate statistically
significant antileukemic activity. For general procedure, see ref 6.
Imidazoacridinones 4 were prepared by hydrazine-
Raney nickel reduction of nitroacridinones 3 to the
corresponding amino derivatives followed by cyclization
with formic acid. The overall process was performed
in different pathways. The usual way was reduction
with hydrazine-Raney nickel in THF (path a). The
reduction products were isolated as the hydrochloride
salts and crystallized from methanol-ether. Since the
obtained hydrochlorides were rather unstable, they were
not characterized but used directly in the cyclization
process. Attempts to reduce the methoxy derivatives
3j,k ,n led to complex mixtures of products. Therefore,
they were hydrolyzed, prior to reduction, by refluxing
with concentrated hydrochloric acid to give products
3o-q selectively deprotected in position 8 (path b).
These compounds were isolated as hydrochlorides,
transformed into free bases, and reduced cleanly with
hydrazine to give the suitable amino derivatives. All
the amino derivatives of compounds 3a -j,l,m ,o-q,u
obtained with paths a and b were transformed in high
yield (95%) into the corresponding imidazoacridinones
4a -h ,k -q,u by refluxing in formic acid. Compounds
3r -t could not be reduced with hydrazine, probably
because of their poor solubility in THF or dioxane. They
were transformed into the corresponding imidazoacri-
dinones 4r -t by a one-pot reduction-cyclization in 80%
formic acid in the presence of nickel aluminum alloy
(path e). All imidazoacridinones were isolated as hy-
drochlorides and crystallized from methanol-ether.
Hydroxy derivatives 4i,j were prepared from the corre-
sponding methoxy compounds 4k ,o in 50% yield by
reaction with boron tribromide-methyl sulfide complex.
Yields and physical properties of the target compounds
4 are reported in Table 2. The structures of the

1030 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5
Cholody et al.
synthesized compounds were established on the basis
of NMR studies, using spin-decoupling methods for
aromatic proton assignment.
sponding 8-hydroxy derivative (compound 4k of ref 2)
and the 8-unsubstituted derivative 5-[[(dimethylamino)-
ethyl]amino]imidazo[4,5,1-de]acridin-6-one (compound
11 of ref 1) are active.
Biologica l Resu lts a n d Discu ssion
To explore the influence of other types of quinones
on biological activity of imidazoacridinones, compounds
with a potential p-quinoid system in ring A were
synthesized. 7,10-Dihydroxy (4j) and 7,10-dimethoxy
(4l) derivatives were found to be inactive, but surpris-
ingly, 7-hydroxy-10-methoxy compounds 4o,p exhibit
significant biological activity. Derivatives bearing a
potential o-quinoid system, namely, 8,9-dimethoxy
(4m ,n ), 7-hydroxy-8,9-dimethoxy (4q), and 8,9-methyl-
enedioxy (4r ,s) imidazoacridinones, also were found to
be inactive. It is worthwhile to note that in mammalian
cells the methylenedioxy group could be metabolized to
catechol.9,10
In conclusion, it can be generalized that the most
promising group of active imidazoacridinones is the
8-hydroxy derivatives, which potentially are able to form
a quinone imine system which probably resulted in
increased ability for covalent binding to DNA. Replac-
ing this potential quinone imine system by potential
quinone systems (ortho or para) resulted in dininish-
ment or loss of biological activity.
The antineoplastic activity of all the synthesized
derivatives of 5-[(aminoalkyl)amino]-6H-imidazo[4,5,1-
de]acridin-6-ones 4a -u was tested in vivo against
murine leukemia P388 (ip/ip: days 1-5). For each
compound a full drug dose-response study was carried
out, with doses ranging from ineffective to toxic. The
optimal dose was defined as that which produced the
highest T/C value. The results obtained at the optimal
dose, a median from three independent tests, are
presented in Table 2. The results, in connection with
those published earlier,1,2 allow to formulate structure-
activity relationships for both side chain and ring A
modifications of 5-[(aminoalkyl)amino]-6H-imidazo-
[4,5,1-de]acridin-6-one derivatives.
The following generalizations concerning the side
chain can be deduced from the data. (1) The distance
between the two amino groups does not seem to be
important for 8-hydroxyacridinones, as even compound
4a , which has a long spacer (five methylene units) in
the side chain, still possesses significant activity. (2)
The proximal amino group does not have to be secondary
as its methylation, as in compounds 4d ,e, does not spoil
activity. (3) Elongation of the side chain by a second
ethyleneamino fragment results in very high activity,
provided that the 8-OH substituent is present (com-
pound 4c). In fact, compound 4b, with identical side
chain but lacking in 8-OH group, has only marginal
activity (T/C of 130%). (4) The significance of bulkiness
of alkyl substituents on the distal amino group is not
clear. Dimethyl and diethyl derivatives are active,2
related di-n-butyl compound 4f is inactive, but, surpris-
ingly, a compound bearing the space-demanding iso-
propyl substituent (4g) is still active. The first two
observations are of special interest as they are in
opposition to those made for related 5-aminotriazolo-
acridinones, for which a secondary proximal amino
group and ethylene or propylene side chain seem to be
obligatory.7
Exp er im en ta l Section
1H NMR spectra of the synthesized compounds were ob-
tained with either a Varian VXR-300 or a Varian Gemini 200
MHz spectrometer, using TMS as an internal standard. NMR
abbreviations used are as follows: br (broad), s (singlet), d
(doublet), t (triplet), qu (quartet), qt (quintet), m (multiplet),
and ex (exchangeable with deuterium oxide). J values are
reported in hertz (Hz). Elemental analyses were performed
by the Laboratory of Elemental Analysis of Department of
Chemical Sciences, University of Camerino, or by Laboratory
of Elemental Analysis, University of Gdansk.
N -(2′,5′-Dim e t h oxyp h e n yl)-6-ch lor o-3-n it r oa n t h r a -
n ilic Acid (1a ). A solution of 11.8 g (0.05 mol) of 2,6-dichloro-
3-nitrobenzoic acid in 100 mL of ethanol was added to 15.5 g
(0.1 mol) of 2,5-dimethoxyaniline and 15 mL (0.1 mol) of
triethylamine. The mixture was refluxed for 100 h under
argon. The solvent was evaporated, and the residue was
dissolved in 2% aqueous solution of Na2CO3, heated to boiling
with charcoal, and filtered after cooling. The filtrate was
acidified with hydrochloric acid, and the orange precipitate was
washed with water, dried, and crystallized from toluene
Substitution pattern of the A ring of the studied
compounds was found to be important. The most
essential was the presence of a hydroxy substituent in
position 8 (compounds 4a ,c,e,g), and in accordance with
the previous results,2 all the compounds were active.
Derivatives having a hydroxy substituent in position 9
(4h ) or 10 (4i) were inactive. It is possible that the
8-hydroxy-substituted compounds are active because,
possessing the OH group in para position to the nuclear
nitrogen of the acridine system, they could be metaboli-
cally transformed into compounds with quinone imine
structures, able to form adducts with DNA. Similar
mechanism of action was found for 8-hydroxyellipticine,
which also has a heterocyclic nitrogen situated in para
position relative to the hydroxy substituent.8 By anal-
ogy with ellipticine, it can also be supposed that the
activity of 8-unsubstituted compounds relies on initial
enzymatic oxidation to the hydroxy derivatives. This
supposition is supported by the findings that substitu-
tion of the position 8 with another group, methyl (4t)
or tert-butyl (4u ), leads to inactive compounds, whereas
in our previous works we have found that the corre-
providing 5.34 g (30%) of 1a , mp 172-174 °C. Anal. (C15H13
-
ClN2O6) C, H, N.
N-(3′,4′,5′-Tr im eth oxyp h en yl)-6-ch lor o-3-n itr oa n th r a -
n ilic Acid (1b). A mixture of 11.9 g (0.065 mol) of 3,4,5-
trimethoxyaniline, 11.8 g (0.05 mol) of 2,6-dichloro-3-nitroben-
zoic acid, 30 mL of ethanol, and 10 mL (0.07 mol) of
triethylamine was heated under reflux 40 h. To the reaction
mixture was added 80 mL of 5 N aqueous solution of NaOH,
and ethanol and triethylamine were distilled off. The orange
sodium salt precipitate was stirred with 200 mL of benzene,
collected, and dried. It was dissolved in 400 mL of water and
acidified with hydrochloric acid. The formed precipitate was
washed with water and crystallized from acetone-water to
give 13.4 g (70%) of red crystals of 1b, mp 212-214 °C. Anal.
(C16H15ClN2O7) C, H, N.
1-Ch lor o-4-n itr o-5,8-dim eth oxy-9(10H)-acr idin on e (2a).
A mixture of N-(2′,5′-dimethoxyphenyl)-6-chloro-3-nitroan-
thranilic acid (1a ) (10 g, 0.028 mol), phosphorus oxychloride
(10 mL), N,N-dimethylaniline (1 mL), and chloroform (50 mL)
was refluxed for 1 h. The solvents were evaporated under
reduced pressure, and the residue was added to a mixture of
acetic acid (50 mL) and water (200 mL) and stirred for 2 h.
The formed red precipitate was filtered and crystallized from
toluene to give 2a (6.7 g, 71%), mp 146-148 °C. 1H NMR

SAR for Antineoplastic Imidazoacridinones
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5 1031
(DMSO-d6): δ 11.8 (1H, s, ex, NH), 8.48 (1H, d, J ) 8.8, C3-
H), 7.24 (1H, d, J ) 8.8, C2-H), 7.11 (1H, d, J ) 8.8, C6-H),
6.67 (1H, d, J ) 8.8, C7-H), 4.06 (3H, s, C5-OCH3), 3.98 (3H,
s, C8-OCH3). Anal. (C15H11ClN2O5) C, H, N.
HCl caused precipitation of product (4k ) as dihydrochloride
salt. 1H NMR (free base) (CDCl3): δ 9.13 (1H, t, ex, NH-CH2),
9.10 (1H, s, C1-H), 8.20 (1H, dd, J o ) 8.1, J m ) 1.2, C7-H),
7.97 (1H, d, J ) 9.0, C3-H), 7.44 (1H, t, J ) 8.1, C8-H), 7.34
(dd, 1H, J o ) 8.1, J m ) 1.2, C9-H), 6.75 (1H, d, J ) 9.0, C4-H),
4.14 (3H, s, 10-OCH 3), 3.48 (2H, qu, NHCH2CH2), 2.84 (2H, t,
NHCH2CH2), 2.66 (4H, qu, N(CH2CH3)2), 1.11 (6H, t, N(CH2-
CH3)2).
5-[[2-(Dieth yla m in o)eth yl]a m in o]-7-h yd r oxy-10-m eth -
oxy-6H-im id a zo[4,5,1-d e]a cr id in -6-on e (4o). 1H NMR (free
base) (CDCl3): δ 13.48 (1H, s, ex, 7-OH), 9.08 (1H, s, C1-H),
8.82 (1H, t, NH-CH2), 7.97 (1H, d, J ) 8.8, C3-H), 7.31 (1H, t,
J ) 8.8, C9-H), 6.87 (1H, d, J ) 8.8, C8-H), 6.78 (1H, d, J )
8.8, C4-H), 4.06 (3H, s, 10-OCH3), 3.68 (2H, qu, NHCH2CH2),
2.96 (2H, t, NHCH2CH2), 2.80 (4H, qu, N(CH2CH3)2), 1.12 (6H,
t, N(CH2CH3)2).
5-[[2-(Dieth ylam in o)eth yl]am in o]-8,9-(m eth ylen edioxy)-
6H-im id a zo[4,5,1-d e]a cr id in -6-on e (4r ). A mixture of 3r
(2 g, 0.005 mol), nickel aluminum alloy (1.5 g), and 80% formic
acid (10 mL) was refluxed with stirring for 20 h. The reaction
mixture was evaporated under reduced pressure and worked
up as described above for 4k . 1H NMR (free base) (CDCl3): δ
9.06 (1H, ex, NH-CH2), 8.44 (1H, s, C1-H), 7.98 (1H, d, J )
8.9, C3-H), 7.92 (1H, s, C10-H), 7.34 (1 H, s, C7-H), 6.77 (1H,
d, J ) 8.9, C4-H), 6.20 (2H, s, OCH2O), 3.51 (2H, qu, NHCH2-
CH2), 2.88 (2H, t, NHCH2CH2), 2.70 (4H, qu, N(CH2CH3)2),
1.15 (6H, t, N(CH2CH3)2).
1-Ch lor o-4-n it r o-6,7,8-t r im et h oxy-9(10H )-a cr id in on e
(2b). This compound was obtain in an analogous manner as
2a . Yield was 85% after crystallization from chloroform-
hexane, mp 242-246 °C. 1H NMR (DMSO-d6): δ 11.30 (1H,
s, ex, NH), 8.46 (1H, d, J ) 8.8, C3-H), 7.48 (1H, s, C5-H),
7.32 (1H, d, J ) 8.8, C2-H), 3.92 (3H, s, OCH3), 3.84 (3H, s,
OCH3), 3.74 (3H, s, OCH3). Anal. (C16H13ClN2O6) C, H, N.
Gen er a l P r oced u r e for th e P r ep a r a tion of 1-[[(Dia l-
k yla m in o)a lk yl]a m in o]-4-n itr o-9(10H)-a cr id in on es 3a -
n ,r -u : 1-[[2-[[2-(Dieth ylam in o)eth yl]am in o]eth yl]am in o]-
4-n itr o-9(10H)-a cr id in on e (3b). A mixture of 1-chloro-4-
nitro-9(10H)-acridinone (2.9 g, 0.01 mol), 2-[(diethylamino)ethyl]-
ethylenediamine (6.3 g, 0.04 mol), and DMF (15 mL) was
stirred and heated at 80 °C for 30 min. Next, a mixture of
acetone and water (v/v 8:2, 100 mL) was added, and the
mixture was left overnight in a refrigerator. The precipitated
solid was filtered off and washed twice with water and
methanol to give pure 3c. 1H NMR (DMSO-d6): δ 12.90 (1H,
s, ex, N10-H), 11.90 (1H, t, ex, NH-CH2), 8.36 (1H, d, J ) 9.9,
C3-H), 8.20 (1H, d, J ) 8.8, C8-H), 7.96 (1H, d, C5-H), 7.78
(1H, t, C7-H), 7.42 (1H, t, C6-H), 6.42 (1H, d, J ) 9.9, C2-H),
3.55 (2H, qu, NHCH2CH2), 2.87 (2H, t, NHCH2CH2), 2.62 (2H,
t, CH2NHCH 2), 2.45 (6H, m, CH2N(CH2CH3)2), 0.95 (6H, t,
N(CH2CH3)2).
5-[[2-(Diet h yla m in o)et h yl]a m in o]-10-h yd r oxy-6H-im -
id a zo[4,5,1-d e]a cr id in -6-on e (4i). To a vigorously stirred
solution of 4k (free base, 1.2 g, 0.0027 mol) in 1,2-dichloro-
ethane (50 mL) was added 1 M solution of BBr3‚Me2S in
dichloromethane (3 mL) slowly at room temperature. The
mixture was refluxed with stirring for 100 h, and during this
time an additional 6 mL of BBr3 complex solution was added
in two portions. The mixture was cooled to room temperature,
the reaction was quenched with ethanol (5 mL), and the
mixture stirred for an additional 30 min. The precipitated
solid was filtered off, dissolved in hot water, and, after cooling,
alkalized using 0.5 N NaOH. The unreacted substrate was
separated by extraction with chloroform; the aqueous solution
was acidified with diluted hydrochloric acid and neutralized
with concentrated ammonia. The precipitated product was
filtered, crystallized from methanol-a few drops of concen-
trated HCl-ether to give hydrochloride of 4i. 1H NMR (free
base) (acetone-d6): δ 11.25 (1H, s, ex, 10-OH), 9.20 (1H, s, C1-
H), 9.10 (1H, t, ex, NH-CH2), 8.01 (1H, d, J ) 8.9, C3-H), 7.90
(1H, dd, J o ) 6.6, J m ) 2.8, C7-H), 7.42 (2H, m, C8-H, C9-H),
6.77 (1H, d, J ) 8.9, C4-H), 3.45 (2H, qu, NHCH2CH2), 2.78
(2H, t, NHCH2CH2), 2.62 (4H, qu, N(CH2CH3)2), 1.05 (6H, t,
N(CH2CH3)2).
1-[[2-(Dieth ylam in o)eth yl]am in o]-5,8-dim eth oxy-9(10H)-
a cr id in on e (3j). 1H NMR (DMSO-d6): δ 12.56 (1H, s, ex, N10-
H), 11.80 (1H, t, ex, NH-CH2), 8.28 (1H, d, J ) 9.7, C3-H),
7.32 (1H, d, J ) 9.0, C6-H), 6.76 (1H, d, J ) 9.0, C7-H), 6.57
(1H, d, J ) 9.7, C2-H), 4.00 (3H, s, 5-OCH3), 3.80 (3H, s,
8-OCH3), 3.60 (2H, qu, NHCH2CH2), 2.80 (2H, t, NHCH2CH2),
2.70 (4H, qu, N(CH2CH3)2), 1.00 (6H, t, N(CH2CH3)2).
1-[[2-(Dieth ylam in o)eth yl]am in o]-6,7-(m eth ylen edioxy)-
9(10H)-a cr id in on e (3r ). 1H NMR (DMSO-d6): δ 12.65 (1H,
s, ex, N10-H), 12.01 (1H, t, ex, NH-CH2), 8.42 (1H, d, J ) 8.9,
C3-H), 7.71 (1H, s, C5-H), 6.86 (1H, s, C8-H), 6.38 (1H, d, J )
8.9, C2-H), 6.14 (2H, s, OCH2O), 3.52 (2H, qt, NHCH2CH2),
2.86 (2H, t, NHCH2CH2), 2.68 (4H, qt, N(CH2CH3)2), 1.12 (6H,
t, N(CH2CH3)2).
Gen er a l P r oced u r e for th e P r ep a r a tion of 1-[[(Dia l-
k yla m in o)a lk yl]a m in o]-8-h yd r oxy-4-n itr o-9(10H)-a cr id i-
n on es 3o-q (Ta ble 1): 1-[[2-(Dieth yla m in o)eth yl]a m in o]-
8-h yd r oxy-5-m eth oxy-4-n itr o-9(10H)-a cr id in on e (3o). A
mixture of compound 3j (2.01 g, 0.05 mol) and concentrated
hydrochloric acid (20 mL) was refluxed with stirring for 3 h.
The solution was cooled down, and the product was precipi-
tated by addition of acetone (60 mL). The precipitate was
filtered off, washed with acetone, dissolved in water, alkalized
with concentrated ammonia, and extracted with chloroform.
The chloroformic solution was dried (MgSO4) and evaporated
to dryness, and the residue was crystallized from chloroform-
hexane to give 3o. 1H NMR (DMSO-d6): δ 12.70 (1H, s, ex,
OH), 12.36 (1H, s, ex, N10-H), 11.26 (1H, t, ex, NH-CH2), 8.40
(1H, d, J ) 9.8, C3-H), 7.07 (1H, d, J ) 8.8, C6-H) 6.60 (1H,
d, J ) 8.8, C7-H), 6.30 (1H, d, J ) 9.8, C2-H), 3.98 (3H, s,
5-OCH 3), 3.50 (2H, qu, NH-CH 2CH2), 2.88 (2H, t, NH-
CH2CH2), 2.70 (4H, qu, N(CH2CH3)2, 1.12 (6H, t, N(CH2CH3)2).
Gen er a l P r oced u r e for th e P r ep a r a tion of 5-[[(Dia l-
k yla m in o)a lk yl]a m in o]-6H -im id a zo[4,5,1-d e]a cr id in -6-
on es 4a -h ,k -q,u (Ta ble 2): 5-[[2-(Dieth yla m in o)eth yl]-
a m in o]-10-m et h oxy-6H -im id a zo[4,5,1-d e]a cr id in -6-on e
(4k ). A suspension of 3i (2.5 g, 0.0065 mol) in THF (50 mL)
was stirred for 30 min at room temperature. Next, Raney
nickel (1 g) followed by hydrazine hydrate (1.3 mL, 0.026 mol)
was slowly added, and the mixture was vigorously stirred for
1 h. The reaction mixture was filtered into THF containing
gaseous HCl (100 mL); the precipitated solid was filtered off
and crystallized quickly from a mixture methanol-ether. The
obtained hydrochloride was dissolved in 95% formic acid (10
mL), and the solution was refluxed with stirring for 20 h. The
reaction mixture was evaporated to dryness under reduced
pressure, and the resulting oily residue was dissolved in hot
methanol and decolorized with charcoal. Addition of ethereal
5-[[2-(Dieth yla m in o)eth yl]a m in o]-7,10-d ih yd r oxy-6H-
im id a zo[4,5,1-d e]a cr id in -6-on e (4j). 1H NMR (free base)
(DMSO-d6): δ 13.48 (1H, s, ex, 7-OH), 10.65 (1H, s, ex, 10-
OH), 9.08 (1H, s, C1-H), 8.82 (1H, t, NH-CH2), 7.97 (1H, d, J
) 8.8, C3-H), 7.31 (1H, d, J ) 8.8, C9-H), 6.87 (1H, d, J ) 8.8,
C8-H), 6.78 (1H, d, J ) 8.8, C4-H), 3.60 (2H, qu, NHCH2CH2),
2.60-2.80 (6H, m, CH2N(CH2CH3)2), 1.12 (6H, t, N(CH2CH3)2).
Ack n ow led gm en t. This work was supported by the
Polish National Council for Scientific Research, Grant
No. 411779101, and by a grant from Italian MURST
(Fondi 40%).
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